Cold conditions may contribute to it, if it makes your media stay too wet, watering it when not needed and all around conditions too cold for the plant. But if it were allowed to stay dry and warm as it went dormant, it should endure overwintering indoors safely, and wake up in mid Spring.
I also do same thing as Karen mentioned, timely chopping off squishy part and allow to dry may help plant survive. But got to keep it warm and dry.
